Optical modulators are optical devices in which signal-controlled elements are used to modulate incident light. Microelectromechanical system (MEMS) based spatial light modulators and electro-optical modulators are two types commonly used optical modulators. A typical MEMS based spatial light modulator comprises an array of mechanically deflectable elements, such as deflectable mirror plates of micromirror devices (e.g. DLP® by Texas Instruments, Inc.) or movable membranes (e.g. IMOD by QualComm, Inc.). Electro-optic modulators are optical modulators whose signal controlled elements exhibit electro-optic effects, based on the effect of which modulations are performed. A typical electro-optical modulator employs nematic materials, which are commonly known as liquid-crystal materials, such as Liquid-crystal-on-silicon (LCoS). A common feature of these nematic materials in existing electro-optical modulators is that the mass centers of nematic molecules have no long range order, and these molecules tend to be parallel to common axes.
Because operations of current MEMS based spatial light modulators are based upon the mechanical movements of deflectable elements (e.g. the mirror plates of micromirror devices); and the mechanical movements often take longer time (e.g. 20 ms or longer) to respond to control signals, performance of the MEMS based spatial light modulators is limited by the slow response time of the mechanical elements. Moreover, mechanical elements often occupy spaces that are much larger than the smallest size of a typical semiconductor circuit (e.g. an addressing electrode and electrical circuit used for deflecting the movable element) achievable by current integrated circuit fabrication technologies. Incorporation of mechanical elements certainly encumbers achieving small size MEMS based spatial light modulators.
Current electro-optical spatial light modulators also have larger response time, which significantly limits their applications. For spatial light modulators based on nematic materials, the response time of the spatial light modulator is determined by the response time of nematic molecules of the spatial light modulator, which is typically in the order of microseconds. The response time of the spatial light modulator can be even larger due to re-orientations of nematic molecules during state transitions. Moreover, the delicate property due to the intrinsic liquid-crystal natural of the nematic based spatial light modulator limits the application of existing nematic based spatial light modulators.
Therefore, it is always desired for spatial light modulators that are preferably robust, reliable, fast, high resolution, and lower power-consumptive.